For many printing and writing grades of paper, a starch solution is applied to the paper surface to enhance the surface strength for end-use applications such as various types of printing. The starch is normally applied at the wet-end (internal sizing) of the paper machine operations and at the size press (external sizing) on the paper machine. The type and amount of starch applied can impact the physical-chemical properties of the paper and the properties of the ultimate end paper product. Thus, a part of the cost of paper manufacturer is related to the cost of the size press starch.
A key property of highly fibrillated surface enhanced pulp fibers is their ability to significantly increase fiber bonding. In this case, the desire is to utilize the strength enhancing and fiber coverage properties of the surface enhanced pulp fibers specifically on the paper surface. The resulting strength increase could then potentially allow a reduction in the amount of starch required while maintaining surface chemistry properties and surface strength. The reduced usage of size press starch would result in a significant cost savings. In the extreme case, an optimal amount of surface enhanced pulp fibers and a minimal amount of starch would be applied to the paper surface with all end use properties maintained.
Pulp fibers, such as wood pulp fibers, are used in a variety of products including, for example, pulp, paper, paperboard, biofiber composites (e.g., fiber cement board, fiber reinforced plastics, etc.), absorbent products (e.g., fluff pulp, hydrogels, etc.), specialty chemicals derived from cellulose (e.g., cellulose acetate, carboxymethyl cellulose (CMC), etc.), and other products. The pulp fibers can be obtained from a variety of wood types including hardwoods (e.g., oak, gum, maple, poplar, eucalyptus, aspen, birch, etc.), softwoods (e.g., spruce, pine, fir, hemlock, southern pine, redwood, etc.), and non-woods (e.g., kenaf, hemp, straws, bagasse, etc.). The properties of the pulp fibers can impact the properties of the ultimate end product, such as paper, the properties of intermediate products, and the performance of the manufacturing processes used to make the products (e.g., papermachine productivity and cost of manufacturing). The pulp fibers can be processed in a number of ways to achieve different properties. In some existing processes, some pulp fibers are refined prior to incorporation into an end product. Depending on the refining conditions, the refining process can cause significant reductions in length of the fibers, can generate, for certain applications, undesirable amounts of fines, and can otherwise impact the fibers in a manner that can adversely affect the end product, an intermediate product, and/or the manufacturing process. For example, the generation of fines can be disadvantageous in some applications because fines can slow drainage, increase water retention, and increase wet-end chemical consumption in papermaking which may be undesirable in some processes and applications.
Fibers in wood pulp typically have a length weighted average fiber length ranging between 0.5 and 3.0 millimeters prior to processing into pulp, paper, paperboard, biofiber composites (e.g., fiber cement board, fiber reinforced plastics, etc.), absorbent products (e.g., fluff pulps, hydrogels, etc.), specialty chemicals derived from cellulose (e.g., cellulose acetate, carboxymethyl cellulose (CMC), etc.) and similar products. Refining and other processing steps can shorten the length of the pulp fibers. In conventional refining techniques, fibers are passed usually only once, but generally no more than 2-3 times, through a refiner using a relatively low energy (for example, about 20-80 kWh/ton for hardwood fibers) and using a specific edge load of about 0.4-0.8 Ws/m for hardwood fibers to produce typical fine paper.